Ecological and geological conditions of the territory of the Urengoy oil and gas condensate field

Abstract

Introduction: needs of ecology-geological conditions research defines by its key role in evolution of lithosphere environmental functions.

Methodology: the characteristics of the ecological and geological conditions are given on the basis of the engineering surveys results during 2015-2021 at the development of Urengoi field facilities. The following ecology-geological conditions went into the questions: geological and geomorphological structure, geocryological conditions, hydrogeological structure. Assessment of the state of phytocenoses has been completed for environmental engineering survey units.

Results and discussion: in geological terms, the most ancient deposits in the research area are opoka, opokamorphic clays and interbedded dense diatomaceous clays of the serovo series of the danian-lutetian stage of the paleocene epoch of the paleogene system with a up to 90 m of layer thickness. The holocene alluvial deposits of floodplain terraces in the form of sand, sandy loam, peat, patchy gravel, pebbles and boulders refer to the most recent formations. Various sites of the field are composed of marine and coastal-marine deposits, lacustrine-marsh, alluvial, lacustrine-alluvial and biogenic formations of recent age were found by the results of geological-engineering boring. As applied to lithology, these are peat, loam, sandy loam and sand. Research area is divided into three conventional zones of permafrost distribution: southern with island, central with intermittent and northern with continuous on the base of engineering and geological conditions. It has been found during summer survey the level of seasonal thawing out is in the depth range of 15−50 cm in the southern part of the field and is in the depth range of 10−57 cm north of the Evo-Yaha river. As applied to hydrogeology, the surveyed area belongs to the Ice (Arctic) macrozone of the first aquifer complex of the оligocene-quaternary deposits from the surface. This aquifer system consists of isolated, vertically oriented narrow troughs of underflow taliks of large rivers, bowl-shaped underflow taliks and rare interpermafrost taliks. The modern vegetation is represented by a combination of sparse forests, tundra and marsh communities, shrub-forb associations and cenoses of anthropogenically transformed habitats at the survey area.

Сonclusion: the analysis revealed that the dominant geocryological conditions influence on the survey area ecosystems functioning. The presence of permafrost soils layer which causes geocryological processes that impede water exchange with underlying horizons, generally indicates the adverse of ecological and geological conditions through the spectacle of the ecological and resource potential of the area.